Behind-the-ear hearing aids wherein sound signals propagate as acoustic signals from a receiver positioned in the hearing aid housing behind the ear and through a sound tube into the ear canal are well known in the art.
In order to position the sound tube securely and comfortably in the ear canal, an earpiece, shell, or earmould is provided for attachment to the sound tube and insertion into the ear canal of the user.
Typically, a first end of the sound tube is attached to a first connector for coupling of the sound tube to the BTE housing containing the electronics of the hearing aid, and a second end of the sound tube is attached to a second connector for coupling of the sound tube to the earpiece. The sound tube is typically flexible so that the sound tube is allowed to bend and provide the required arcuate propagation path of the sound from the receiver output.
In the BTE hearing aid disclosed in EP 1 448 014, the sound tube has a pre-formed shape that includes a first bend extending from the first connector over the top of the ear of the user and a second bend extending from an outside of the ear into an ear canal of the user when the hearing aid is worn by the user.
It is also known to manufacture the sound tube with the first and second connectors in one unit in different standard sizes, for example with different lengths between the first and the second bend, e.g. 4 different lengths, and different lengths between the second bend and the earpiece, e.g. 2 different lengths, to fit the human anatomy of the ear of most users. Further, the sound tubes may be fitted with earpieces or shells of different sizes e.g. 3 different standard sizes, or custom mold. Finally, the sound tube has to be manufactured with bends adapted to the right ear and bends adapted to the left ear. The present example leads to 48 (4*2*3*2) standard sizes of the unit to be manufactured and to be kept in stock by the hearing aid dispensers. Still further, the sound tube may be delivered with various diameters.
In WO 99/04601 a method of producing a sound tube with a pre-formed shape is disclosed, comprising the steps of overmoulding a connector member and an earpiece to respective ends of the sound tube, positioning of a formed wire within the tube, thus bending the tube to the desired shape, heating of the tube with the wire to about 120° C. to shape the tube, cooling, and removal of the wire. Upon cooling, the tube retains the shape of the wire.
This method is cumbersome, slow and labour intensive. Thus, there is a need for a more expedient and cost effective method of producing a sound tube with a pre-formed shape.